a) Field of the Invention
The present invention concerns a brake-adjusting system, in particular for motor-vehicle hand or emergency brakes, comprising a brake lever, an actuating element for the brake, a system sub-assembly to adjust the effective length of the brake cable including two freewheel uniting devices. At least one freewheel uniting device locks in geometric manner the relative position of brake lever to the actuating element under brake tensioning. Further, at least three stops are provided to adjust the path of the actuating element; the freewheel uniting device being mounted between two of the three stops of the said system sub-assembly.
b) Description of Related Art
A similar adjusting system is known from the German Offenlegungsschrift 41 09 887 wherein two pawl mechanisms oriented in the same direction and mounted in a common and essentially cylindrical housing are used as the freewheel unit device. A double stop in the form of a housing wall enclosing a drawbar is present between the two freewheel units and provides a rest for clamping parts of both freewheel units alternatingly resting on it at opposite sides. A further stop limits the second final position, determined by the needs of the braking system, of the first freewheel unit and forms a sort of pre-chamber in the housing to determine the slack of the brake. The two freewheel units are co-directional, that is, they lock in the same direction. When the brake is actuated, the second freewheel unit will lock by a set of teeth with the driving element, while the clamping part of the first freewheel unit will slip over the actuating element as soon as it has passed through the slack of the pre-chamber and come to rest against the double stop.
The kinetic sequence is reversed when disengaging the brake. The first freewheel unit with its elastically compressed clamping part passes through the pre-chamber until coming to rest against the opposite stop and at the latest will lock there with the actuating element in the form of a drawbar and shall prevent further displacement of the actuating element. Further displacement of the brake lever causes the clamping part of the second freewheel unit to slip on the actuating element. Thereby the effective length of the brake linkage or brake cable is shortened by the excess play or the excess of slack. The desired amount of slack is set by the play of the first freewheel unit in the pre-chamber. Preferably this design is applied to motor-vehicle handbrakes.
The known design offers the advantage of also allowing automatically adjusting the brake when it is actuated, however this automatic adjustment entails some dangers. When adjusting, no means is provided to check whether the extent of permissible adjustment already was exceeded. Another drawback is that when overloading the brake by the handbrake, insufficient slack might be set and that when the brake return-spring fails, the required amount of slack also may be lost. Lastly the cylindrical housing for quick-adjustment may be too large to be accommodated in every drive shaft housing. Furthermore an adjusting system for railroad-car brakes operating on similar principles already is known from the German patent 671,006.